Method of separating precious metals and copper from cyanide solution



Patented Jan. 15, 1929.

UNITED STATES PATENT OFFICE.

LIONEL H. DUSOHAK,

TIN'UOUS FILTER COMPANY, OF FORNIA.

OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO OLIVER CON- OAKLAND, CALIFORNIA, A CORPORATION OF CALI- METHOD OF SEPARATING PRECIOUS METALS AND COPPER FROM OYANIDE SOLUTION.

No Drawing.

This method relates to the separate precipitation of precious metals and copper from cyanide solutions, and its object is to provide for the recovery of the precious metals and copper in as pure forms as possible, without the necessity of extended subsequent treatment of a base bullion, which treatment is necessary where the precious metals and copper are separated from the.

1 solution in one operation. It will be understood by those skilled 1n the art, that in the treatment of copperbearing precious metal ores by the cyanide process, that considerable difliculty is caused by the copper which is dissolved in the cy anide solution. When zinc is the rprecipitant used for the precious metals the copper also precipitates on the zinc, and renders it ineffective, or less effective, as a precipltant for the precious metals, thereby reducing the. capacity of using up the precipitating agent needlessly and wasting cyanide; and to avo1d a loss of cyanide the copper must be precipitated to 2 release cyanide for further use in leachlng the ore.

Either zinc dust or zinc shavings are com- I monly used as the precipitating agent, and as thecopper precipitates with the preclous metals, the resulting bullion is low grade,

and it becomes necessary to refine, at considerable expense, this ow grade bullion. It would obviously be less expensive to be able to precipitate the precious metals and copper separately, for then each could be smelted with little loss.

I have found that by the use of an amalgam containing one or more metals, such as sodium or zinc, that the precious metals and copper can be separately precipitated, provided the inherent properties of precipitation of the precious metals and copper are considered. A

I have discovered that the rate of precipitation of the precious metals from the cyanide solution with the use of such amalgams, is many times greater than the rate 'of precipitation of copper, and that the resence of copper n the cyanide solution oes not interfere either wlth the rate or completeness of precipitation of the precious metals.

Therefore in carrying out this process the cyanide solution containing preciou" metals,

the apparatus. as well as Application filed October 1, 1925. Serial No. 59,813.

and the copper is first brought into contact for a short period with an amalgam such as;

zinc or sodium with mercury which contact is continued only long enough to remove the addition of any fresh cyanide to the solution to brin it up to the desired standard, is then su jected to a considerably longer contact with a separate portion of amalgam with which the copper is precipitated.

The cyanide solutionfrom which the pre-, cious metals and copper have been removed, is now available for use in treating a new lot of ore with the same advantage as to the regeneration of the sodium or potassium solution, as ,if the several metals were precipitated by such amalgam at one time. o

The time required for carrying out the two stages of precipitation will depend upon the way in which the pregnant solution and amalgam are brought into contact with one another, but it maybe stated that the time needed for the recipitation of the precious metals will be rom one-tenth to one-twentieth of the time required for the precipitation of the copper.

It will be understood that the treatment of ore by the cyanide process is essentially a cyclic operation, the steps 'of which are as follows: 7 i n First: Leaching of the ore.

Second: Precipltation of the values from the pregnant solution, and then using the barren solution for repetition of the process.

. Whatever copper may be dissolved, may

either be all precipitated each time or may be allo wed to accumulate in the solution if its content is not too great, through several precious metal precipitations. Ordinarily a balanced operation will be found convenient,

the copper precipitating circuit being proportioned to the main clrcuit in such. a way thatall of the copper will be removed in one place, while all of the preciousmetals are removed from the solution in another place. This method makes it possib1e' to treat considerable tonnages of copper-bearing precious metal ores, which cannot be successfully 5 treated ordinarily.

Experiments shows that to carry out this process the amalgam used must be electropositive with respect to copper. It ,is of course understood that all amalgams contain 1 a certain percentage of mercury as one of the constituents thereof.

What I claim is as follows, but modifications may be made in the above particular described form of the invention within the 15 purview thereof:

' maaato precious metals there rom, and thereafter treating the solution with a separate portion of an amalgam of the same character for a longer period to remove the copper and reusing the treated solution to treat a fresh quantity of ore.

In testimony whereof I have hereunto set my hand this 29th day of August, A. l). 1925. LIONEL H. ,DUSCHAK. 

